Cooking for Geeks: Real Science, Great Hacks, and Good Food

by Jeff Potter

  Add 1 to 1½ cups broth or stock; whisk to combine. Simmer over low heat for several minutes, until the gravy has reached your desired thickness. If the gravy remains too thin, add more flour. (To prevent clumping, create a slurry by mixing flour with cold water, and add that.) If the gravy becomes too thick, add more liquid.

  Cornstarch

  Create a cornstarch paste by mixing 2 tablespoons (16g) cornstarch with ¼ cup (60g) cold water.

  In a saucepan, heat up 1 to 1 ½ cups broth or stock. Add the cornstarch and simmer for 8 to 10 minutes to cook the cornstarch. If the gravy remains too thin, add more cornstarch paste. If the gravy becomes too thick, add more liquid.

  Notes

  You can use the drippings from roasted meats, such as turkey or chicken, to bring more flavor to the gravy. If using flour, substitute the fat in the drippings for the butter. If you’re searing a piece of meat, use the same pan for making the gravy, deglazing it with a few tablespoons of wine, vermouth, Madeira, or port to loosen up the fond that will have formed on the surface of the pan.

  Try sautéing some mushrooms and adding them into the gravy as well. Or, if you’re cooking a turkey, slow-cook the turkey neck a day in advance and pull off the meat and add it into the gravy as well.

  Making Things Melt in Weird Ways: Methylcellulose and Maltodextrin

  At a high level, making gels is about transforming liquids into solids. In addition to creating gels, though, modern food additives can be used to alter other properties of foods, and another area of play in the modernist kitchen is that of melting. How can we make things change state in unexpected ways?

  "Melts" as it cools: Methylcellulose

  Methylcellulose has the unusual property of getting thicker when heated (thermo-gelling in chem-speak). Take jam: when heated, it loses its gel structure (the pectin melts), causing it to flow out of things like jam-filled pastries. Adding methylcellulose prevents this by causing the jam to "gel" into a solid under heat. And since methylcellulose is thermoreversible, upon cooling after baking, the jam returns to its normal consistency.

  Note

  Hollywood uses methylcellulose to make slime. Add a bit of yellow and green food dye, and you’ve got yourself Ghostbusters-style slime. To get good consistency, whisk it vigorously to trap air bubbles into the mixture.

  Methylcellulose has been used in some modernist cuisine dishes for its thermo-gelling effects. One famous example is "Hot Ice Cream" in which the "ice" cream is actually hot cream that’s been set with methylcellulose. As it cools to room temperature, it melts.

  Instructions for use. Dissolve methylcellulose into hot water (above 122°F / 50°C) and then whisk while cooling down. Mixing it directly in cold water can be difficult because the powder will clump up as it comes into contact with water. In hot water, though, the powder doesn’t absorb any water, allowing it to be uniformly mixed. It’s easiest to stir in 1.0% to 2.0% (by weight) into your liquid and let it rest overnight in the fridge to dissolve fully. You can then experiment with setting the liquid. Try baking a small dollop of it, or dropping it by the ice cream scoopful into a pan of simmering water.

  Uses. Commercial applications use it to prevent "bake-out" of fillings in baked goods. Methylcellulose also has high surface activity, meaning that it acts as an emulsifier by keeping oil and water from separating, so it is also used in low-oil and no-oil dressings and to lower oil absorption in fried foods.

  Note

  Methylcellulose increases surface tension—well, actually, "interfacial tension" because "surface" refers to a two-dimensional shape—which is why it works as an emulsifier.

  Origin and chemistry. Methylcellulose is made by chemically modifying cellulose (via etherification of the hydroxyl groups). There can be great variation between types and derivatives of methylcellulose, in terms of thickness (viscosity), gelling temperature (122–194°F / 50–90°C), and strength of gel (ranging from firm to soft). If you’re having problems getting your methylcellulose to set, check the specifications of the type you have. See Linda Anctil’s primer at http://www.playingwithfireandwater.com/foodplay/2008/03/methylcellulose.html for additional details.

  When cold (on left), water molecules are able to form water clusters around the methylcellulose molecule. With sufficient heat—around 122°F / 50°C—the water clusters are destroyed and the methylcellulose is able to form crosslinks, resulting in a stable gel at higher temperatures.

  Hot Marshmallows

  These marshmallows remain firm when hot, but melt as they cool. This recipe is adapted from a recipe by Linda Anctil (http://www.playingwithfireandwater.com).

  In a saucepan, bring to a boil:

  2⅛ cups (500g) water

  1 cup (200g) sugar

  Let cool, and then whisk in:

  10g methylcellulose (use a scale to ensure an accurate measurement)

  1 teaspoon (5g) vanilla extract

  Let rest in fridge until thick, around two hours. Once thick, whisk until light and foamy. Transfer to a 9″ × 9″ / 20 cm × 20 cm baking pan lined with parchment paper. Bake for five to eight minutes at 300°F / 150°C, until set. The marshmallows should feel dry to the touch and not at all sticky. Remove from oven, cut into desired shapes, and coat with powdered sugar.

  Two marshmallows on a plate of powdered sugar.

  Two marshmallows after being coated with powdered sugar while still hot.

  Same marshmallows after cooling for a few minutes.

  When working with gels, you can quickly cool the hot liquid by whisking it while running cold water over the outside of the pan. The water will flow along the bottom of the pan.

  "Melts" in your mouth: Maltodextrin

  Maltodextrin—a starch—dissolves in water, but not fat. In manufacturing, it’s spray-dried and agglomerated, which creates a powder that’s very porous on the microscopic level. Because of this structure, maltodextrin is able soak up fatty substances (they won’t cause it to dissolve), making maltodextrin useful for working with fats when designing food. It also absorbs water, so is used as an emulsifier and thickener, as well as a fat substitute: once hydrated, it literally sticks around, mimicking the viscosity and texture of fats.

  Since it comes as a white powder, you can also use maltodextrin to turn fatty liquids and solids such as olive oil and peanut butter into powder. Because maltodextrin traps oils but dissolves in water, the resulting powder dissolves in your mouth, effectively "melting" back into the original ingredient and releasing its flavor. Since maltodextrin itself is generally flavorless (only slightly sweet), it does not substantially alter the flavor of the product that is being "powderized."

  In addition to the novelty and surprise of, say, a powder dusting on top of fish melting into olive oil in your mouth, powders can carry flavors over into applications that require the ingredients to be effectively "dry." Think of chocolate truffles rolled in chopped nuts: in addition to providing flavor and texture contrast, the chopped nuts provide a convenient "wrapper" around the chocolate to allow you to pick up the truffle and eat it, without the chocolate ganache melting on to your fingers. Powdered products can be used to coat the outsides of foods in much the same way that chopped nuts are used to coat the outside of truffles.

  Instructions for use. Add powder slowly to your liquid fat for a ratio of about 60% fat, 40% maltodextrin by weight. You can pass the results through a sieve to change the texture from breadcrumb-like to a finer powder.

  Uses. Industry commonly uses maltodextrin as a filler to thicken liquids (e.g., the liquid in canned fruits) and as a way to carry flavors in prepackaged foods such as flavored chips and crackers. Since it traps fats, any fat-soluble substances can be "wicked up" with maltodextrin and then more easily incorporated into a product. For experimental dishes, you can use maltodextrin to create powders that can be sprinkled on the plate as garnish or as a way of transforming something that’s normally liquid into a solid.

  Origin and chemistry. Derived from starches such as corn, wheat, or tapioca. Tapioc
a maltodextrin seems to be most commonly used in modernist cooking. Maltodextrin is made by cooking down the starches and running the resulting hydrolyzed starches through a spray-dryer. Chemically, maltodextrin is a sweet polysaccharide composed of typically between 3 and 20 glucose units linked together.

  When it comes to understanding how maltodextrin soaks up oils, imagine it being like sand at the beach. The sand doesn’t actually bond with the water, but it’s still wicking up the liquid in the space between the granules due to capillary action. When working with either sand or maltodextrin, with the right amount of liquid, the powder clumps up and becomes workable. Because maltodextrin is water soluble, however, water would dissolve the starch granules. And, luckily, maltodextrin can soak up a lot more oil per volume than sand can soak up water, making it useful for conveying flavors in a nonliquid form.

  Powdered Brown Butter

  Whisking any fat such as browned butter (upper left) with maltodextrin (center right) creates a powdered form (bottom) that can be used to create a surprising texture as the powder "melts" back into browned butter when placed in the mouth. Try using this browned butter powder as a garnish on top of or alongside fish, or making a version with peanut butter and sprinkling on desserts.

  In a skillet, melt:

  4 tablespoons (60g) salted butter

  Once melted, continue to heat until all the water has boiled off. The butter solids will start to brown. Once the butter has completely browned and achieved a nutty, toasted aroma, remove from heat and allow to cool for a minute or two.

  In a small mixing bowl, measure out:

  ½ cup (40g) maltodextrin

  While whisking the maltodextrin, slowly dribble in the browned butter until a wet sand–like consistency is reached.

  Notes

  Stir slowly at the beginning because maltodextrin is light and will easily aerosolize. The ratio between maltodextrin and the food will vary. If your result is more like toothpaste, add more maltodextrin.

  If the resulting powder is still too clumpy, you might be able to dry it carefully by transferring the powder to a frying pan and applying low heat for a few minutes. This will help dry out any dampness present from room humidity. It will also partially cook the food item, which might not work for powders containing items such as white chocolate.

  For a finer texture, try passing the powder through a sieve or strainer using the back of a spoon.

  Try adding a bit of lemon juice to the brown butter, after it has cooled but before mixing it with the maltodextrin.

  Additional flavors to try: peanut butter, almond butter, coconut oil (virgin/unrefined), caramel, white chocolate, Nutella, olive oil, foie gras, bacon fat (cook some bacon and save the fat drippings—this is called rendering). You don’t need to heat the fats first, but it might take a bit of working to get the maltodextrin to combine. For liquid fats (olive oil), you will need to use roughly 2 parts maltodextrin to 1 part fat: 50g olive oil, 100g maltodextrin.

  Making Foams: Lecithin

  Foams are another area of play in modernist cuisine. If you ever happen to be served a dish that has a "foam" component—say, cod served on a bed of rice with a "carrot" foam or uni (sea urchin) in a shell with green apple foam, it was probably created by adding a stabilizer such as lecithin or methylcellulose to a liquid and then whipping or puréeing it. (Foams can also be created using cream whippers as described in Cream Whippers (a.k.a. "iSi Whippers") in Chapter 7.) While perhaps a little too trendy, it’s a clever way to introduce a flavor to a dish without adding much body.

  Instructions for use. Add about 1% to 2% lecithin to your liquid (by weight, i.e., 1g lecithin per 100g liquid) and use an immersion blender to froth the liquid. Hold the immersion blender up and at a slight angle so that the blades are in contact with both the liquid and air.

  Uses. As an emulsifier, lecithin can be used to create stable flavored foams. It’s also used as an antispattering agent in margarines, an emulsifier in chocolate (to reduce the viscosity of the melted chocolate during manufacturing), and as an active ingredient in nonstick food sprays.

  Origin and chemistry. Lecithin is typically derived from soya beans as a byproduct of creating soy-based vegetable oil. Lecithin is extracted from hulled, cooked soya beans by crushing the beans and then mechanically separating out (via extraction, filtration, and washing) crude lecithin. The crude lecithin is then either enzymatically modified or extracted with solvents (e.g., de-oiling with acetone or fractionating via alcohol). Lecithin can also be derived from animal sources, such as eggs and animal proteins, but animal-derived lecithin is much more expensive than plant-derived lecithin, so it is less common.

  Lecithin molecules have polar and non-polar regions that are most stable when one side is exposed to a polar substance and the other side to a nonpolar substance. See the sidebar The Chemistry of Emulsifiers for a description of how lecithin stabilizes foams.

  Fruit Juice Foam

  In a large mixing bowl or other similarly large and flat container, blend with an immersion blender:

  ½ cup (100g) water

  ½ cup (100g) juice, such as carrot, lime, or cranberry

  1 teaspoon (3g) lecithin (powder)

  Notes

  Hold the immersion blender such that it is partly out of the liquid. You want to allow it to siphon air into the mixture.

  Allow foam to rest for a minute after blending, so that the resulting foam that you spoon off is more stable.

  Try other liquids, such as coffee or beet juice. Lecithin works best at around a 1–2% concentration (2g lecithin per 100g of liquid).

  Lecithin can be used to make a large-bubble foam that is surprisingly stable for long periods of time.

  The Chemistry of Emulsifiers

  You might be wondering why oil and water are able to "mix" in the presence of an emulsifying agent, after the earlier discussion about polar (e.g., water) versus non-polar (e.g., oil) molecules not being able to mix. An emulsifier has a hydrophilic/lipophilic structure: part of the molecule is polar and thus "likes" the water, and part of the molecule is nonpolar and "likes" the oil. Emulsifiers concentrate at the boundary between water and oil because of the charge structure of the molecules.

  Adding an emulsifier keeps foods from separating by providing a barrier between droplets of oil. Think of it like a skin around the oil droplets that prevents different droplets from touching and coalescing. Emulsifiers reduce the chance that oil droplets will aggregate by increasing what chemists call interfacial tension. The oil and water don’t actually mix; they’re just held apart at the microscopic level.

  Emulsifiers stabilize foams by increasing their kinetic stability—i.e., the amount of energy needed to get the foam to transition from one state to another is higher. Take the foam of a bubble bath as an example: the soap acts as an emulsifier, creating a foam of air and water. Water doesn’t normally hold on to air bubbles, but with the soap (the emulsifier), the interfacial tension between the air and water goes way, way up, so it takes more energy to disrupt the system. The more energy it takes, the more kinetically stable the foam is, and the longer it’ll last.

  Take a look at the following two photographs to see what a difference an emulsifier can make (and see http://www.cookingforgeeks.com/book/lecithin/ for a video demonstration).

  A photo under a light microscope of a half-water, half-oil solution. (The slide is pressing the oil droplets flat.)

  The same mixture with 1% lecithin added. The droplets are stable and do not coalesce into larger drops.

  Anti-Sugar: Lactisole

  This one is unusual. Unlike the modern additives covered so far, which have essentially focused on either trapping liquids in a gel structure or changing the physical state of food, "anti-sugar" is an additive used to modify a flavor sensation: it reduces the sensation of sweetness. (And no, mixing sugar and anti-sugar does not result in more energy being released than eating just plain sugar.)

  One of the challenges facing the food industry is the need to max
imize shelf stability and storage potential while maintaining acceptable flavor and texture. Sugar is used in confections and sweets not just for its sweetness, but also as a preservative: because sugar "latches" on to water, it reduces the amount of water available in a food product for bacterial growth. Think back to the FAT TOM rule from Chapter 4: bacterial growth is inhibited by reducing the water activity (the "M" in FAT TOM is for moisture), and because sugar is hygroscopic, adding sugar reduces the freely available water. But more sugar means increased sweetness, so the other flavors in foods can end up being masked with a cloying, overly sweet taste.

  In the mid-1990s, Domino Sugar researched chemical modifiers that would reduce the perception of sweetness. The compound lactisole—a carboxylic acid salt—happens to do just that: add it to your foods at a concentration of around 100 parts per million (ppm), and goodbye sweet sensation, as it interferes with your taste buds (the TAS1R3 sweet protein receptor, for you bio geeks). Unlike traditional methods of dampening sweetness in a dish (i.e., adding bitter or sour ingredients), lactisole works by inhibiting the sensation of sweetness on the tongue, so it does not impact perception of saltiness, bitterness, or sourness. Sadly, you can’t add it to foods to remove the calories from sugar.